Heretofore, as a working medium for heat cycle such as a refrigerant for a refrigerator, a refrigerant for an air conditioner, a working fluid for power generation system (such as exhaust heat recovery power generation), a working medium for a latent heat transport apparatus (such as a heat pipe) or a secondary cooling medium, a chlorofluorocarbon (CFC) such as chlorotrifluoromethane or dichlorodifluoromethane, or a hydrochlorofluorocarbon (HCFC) such as chlorodifluoromethane has been used. However, influences of CFCs and HCFCs over the ozone layer in the stratosphere have been pointed out, and their use is regulated at present.
Accordingly, as a working medium for heat cycle, a hydrofluorocarbon (HFC) which has less influence over the ozone layer, such as difluoromethane (HFC-32), tetrafluoroethane or pentafluoroethane, has been used. However, it has been pointed out that HFCs may cause global warming. Accordingly, development of a working medium for heat cycle which has less influence over the ozone layer and has a low global warming potential is an urgent need.
For example, 1,1,1,2-tetrafluoroethane (HFC-134a) used as a refrigerant for an automobile air conditioner has a global warming potential so high as 1,430 (100 years). Further, in an automobile air conditioner, the refrigerant is highly likely to leak out to the air e.g. from a connection hose or a bearing.
As a refrigerant which replaces HFC-134a, carbon dioxide and 1,1-difluoroethane (HFC-152a) having a global warming potential of 124 (100 years) which is low as compared with HFC-134a, have been studied.
However, with carbon dioxide, the equipment pressure tends to be extremely high as compared with HFC-134a, and accordingly there are many problems to be solved in application to all the automobiles. HFC-152a has a range of inflammability, and has a problem for securing the safety.
As a working medium for heat cycle which has inflammability suppressed, has less influence over the ozone layer and has less influence over global warming, a hydrochlorofluoroolefin (HCFO) such as a hydrochlorofluoropropene, or a chlorofluoroolefin (CFO), which has a large proportion of halogen to suppress inflammability and has a carbon-carbon double bond which is easily decomposed by OH radicals in the air, is conceivable.
As a hydrochlorofluoropropene, for example, 1-chloro-3,3,3-tetrafluoropropene (E) (HCFO-1233zd(E)) is known (Patent Document 1).
However, in a case where HCFO-1233zd(E) is used as a working medium for heat cycle, the cycle performance (efficiency) is insufficient.